Re: [Patch v2 3/3] xen/gdbsx: Security audit of {, un}pausevcpu and domstatus hypercalls

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 24/07/14 13:58, Jan Beulich wrote:
>>>> On 24.07.14 at 13:16, <andrew.cooper3@citrix.com> wrote:
>> --- a/xen/arch/x86/domctl.c
>> +++ b/xen/arch/x86/domctl.c
>> @@ -1030,11 +1030,10 @@ long arch_do_domctl(
>>          if ( !d->controller_pause_count )
>>              break;
>>          ret = -EINVAL;
>> -        if ( domctl->u.gdbsx_pauseunp_vcpu.vcpu >= MAX_VIRT_CPUS ||
>> +        if ( domctl->u.gdbsx_pauseunp_vcpu.vcpu >= d->max_vcpus ||
> As mentioned on IRC - are you sure you can replace (rather than
> amend) the previous bounds check? I.e. do you _know_ that gdbsx
> can deal with guests having more than MAX_VIRT_CPUS vCPU-s?
>
> Jan
>

I have no idea whether it can or not, but if it asks for a legitimate ID
greater than MAX_VIRT_CPUS, then I think it is reasonable to assume yes.

~Andrew